Methyl .alpha.-methyl-.beta.-acylthiopropionates are important intermediates for the synthesis of pharmaceutical agents. For instance, Captopril (1-(3-mercapto-2-D-methyl-propanoyl)-L-proline), an orally active angiotensin converting enzyme inhibitor used in treating hypertension, is synthesized from a D-(-)-.alpha.-methyl-.beta.-acylthiopropionate.
Methods for preparing .alpha.-methyl-.beta.-acylthiopropionates have been reported in the literature. S-T. Chen et al. (1989) J. Chin. Chem. Soc., Vol. 36, pages 451-458, for example, describes preparation of .alpha.-methyl-.beta.-acylthiopropionates by an addition reaction between a thiocarboxylic acid, e.g., thiobenzoic acid, with methyl methacrylate. Under the described reaction conditions, however, at least 24 hours is required for the reaction to reach completion and excessive amounts of methyl methacrylate, a toxic reagent, is employed. Accordingly, a simple and economical method for preparing .alpha.-methyl-.beta.-acylthiopropionates which eliminates the aforementioned deficiencies is needed in the art.